New Zealand’s Labour party is about to reveal its first budget in nearly a decade after last year’s sensational election result but the big news to start the day was: what would the finance minister eat before his speech?

Cue the prime minister, Jacinda Ardern, with one of her informal but popular Facebook Live videos. Via a greasy iPhone lens, she introduces the finance minister, Grant Robertson, about to tuck into a cheese roll, a gooey cheese mixture melted in a slice of white bread.

Scandal? Not so much but it does break with a longstanding tradition of eating a pie instead. Eating a “budget snack” became a tradition under the previous long-serving National government, with finance minister Bill English always going for a pie.

This year, Robertson has chosen to snack on cheese rolls, in a nod to his South Island roots. Cheese rolls are a regional dish from the far south, and the cheese mixture grilled into rolled white bread also often features mustard powder, canned cream, dried onion soup mix and red onion.

“There’s always this odd tradition of people asking what you eat before the budget,” says Ardern to Robertson in the Facebook video. “I don’t know where that originated from.”

“I am not sure either,” says Robertson, smiling as he gestured with his chosen meal. “I think Bill English used to eat a pie, and I think we concluded that I eat too many pies already so we had to come up with a different snack and in a nod to my southern roots: cheese rolls, excellent cheese rolls.”

“They are excellent cheese rolls,” agrees Ardern, who is a month away from expecting her first child. “The only thing I am disappointed in is that they weren’t bought here by your mum,” she adds, who later pans around to include the finance minister’s mother in the background.

National party supporters tweeted that they would still be eating pies.

New Zealanders reacted with amusement to Robertson’s shake-up of the budget snack, though some suggested the choice – sometimes referred to as “southern sushi” – could be healthier. “Did Mr Robertson pay for the cheese rolls? Or the taxpayers?” asked one commenter on Facebook. Another said: “I hope you put enough of those in the budget for everyone Grant.”

Other New Zealand traditions on budget day include what tie the finance minister chooses, and getting a haircut before the announcement.

Robertson said he had a haircut last week because he didn’t like the fresh haircut look, and the prime minister had given him a tie for budget 2018. “I have gifted Grant a tie to try and release some of the stress of picking a tie on budget day,” said Ardern.